Whoa, whoa, wait...
From the point of view of old clients, segwit adds one coinbase output that contains the root hash of the Merkle tree that commits to the witness transaction ids. It uses 47 extra bytes per block, so technically, yes, it "wastes precious blockchain space".
So, 47 bytes per block. That's not too unreasonable. But...
This then gets us to my question that is not being answered. On average, how many bytes in the blockchain will be needed for a standard payment sent via segwit?
Is this ever less than it would be now?
Is this ever the same as it is now?
Is this usually about 50 bytes more per tx?
50 bytes per transaction for fully-validating nodes? This needs to be answered.
I would like to see an answer to this too, it seems everyone is avoiding this question. Fully validating nodes are very important for those of us that want to verify the blockchain ourselves and are required for bootstrapping new nodes.